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Old 09-23-2012, 12:05 AM   #1
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Noise when decelerating?

Just bought a 95 YJ 2.5L w/a 5speed on 31inch tires w/ no lift stock suspension. It has 77,000 miles and drives great otherwise. It's my 2nd YJ (my 1st was a stock 4.0 also a 5speed). My question is, when decelerating and letting foot off gas pedal, I hear a grinding/whining noise that goes away when i give it gas. Also, while sitting in traffic idling in neutral, there is a noticable vibration that goes away when i give it gas. Dont see any leaks underneath. Are 4cyl YJs just louder and ride differently than the 6cyl YJs? Is it my 31s w/ no lift? Any ideas?

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Old 09-23-2012, 12:52 AM   #2
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The four banger has valve train noise standard and vibrates more in stock form. But a grinding noise is not normal. The quick guess for your description could be a dry pilot bearing which is located in the flywheel and part of a clutch kit. But the noise could be a whole lot of other things.

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Old 09-28-2012, 04:42 PM   #3
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I found a video on youtube with a guy who had a dodge truck w/ a manual trans that made the same exact noise as my YJ, which you can really hear after you let off on the gas pedal at all speeds and gears. He found that it was his wheel bearing that needed to be replaced. Are the wheel bearing and pilot bearing the same part?
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Old 09-28-2012, 05:30 PM   #4
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Mine does the same thing. I found a few places that said it was that their pinion nut had backed off. I took my driveshaft off and checked it. Mine was good, so it's something else, but you could always give tours a look to see if it something simple... My YJ is a 6cyl, I don't think it has anything to do with the size of the engine... I'm still looking for ideas myself... I can't seem to figure mine out...
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Old 09-28-2012, 09:27 PM   #5
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Mine had same symptoms but when i took the cover off the rear end the pinon gear was almost gone.. put an ford 8.8 rear in and no more grinding sound
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Old 09-29-2012, 06:17 AM   #6
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Mine had same symptoms but when i took the cover off the rear end the pinon gear was almost gone.. put an ford 8.8 rear in and no more grinding sound
That's going to be my winter project. I have the 8.8 w/LSD and the matching D30 gears in the garage waiting on me right now.
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Old 09-29-2012, 09:34 AM   #7
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Originally Posted by chamojeep1995 View Post
I found a video on youtube with a guy who had a dodge truck w/ a manual trans that made the same exact noise as my YJ, which you can really hear after you let off on the gas pedal at all speeds and gears. He found that it was his wheel bearing that needed to be replaced. Are the wheel bearing and pilot bearing the same part?
No, they are not the same part. The wheel bearing is a part of the axle assembly.

I would suggest that it could be also the pinion bearing, but that requires someone who knows what to look for doing the troubleshooting.

What is your level of expertise or mechanical ability, say between 1 and 5 being 1 is poor, and 5 is exceptional?

Its not a difficult job taking some things apart to verify where/what bearing is a problem. If you do tackle it, take lots of pictures, and you could even post some if you have any questions. Assuming you want to do the work.
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Old 09-29-2012, 11:16 AM   #8
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I do all the routine maintenance (all fluid checks and replacement of filters plugs hoses etc) but never had to take anything apart, although I'm not afraid of doing it if need be. Is this something where i will need to take the entire rearend off my Jeep to fix?
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Old 09-29-2012, 11:22 AM   #9
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I do all the routine maintenance (all fluid checks and replacement of filters plugs hoses etc) but never had to take anything apart, although I'm not afraid of doing it if need be. Is this something where i will need to take the entire rearend off my Jeep to fix?
No, just jack it up and support it very well.

I do one side at a time, and it is basically just pulling the wheel, pull the diff cover, remove the pin in the carrier (kinda tricky), push the axle in and pull the "C" clip, then pull the axle out. Assuming you do not have an older axle that is a non "C" clip version.

Inspecting the axle real carefully where the bearing rides, and the bearing; any pits grooves and the like and the axle/bearing is bad. Depending on the damage and the wear (mileage), you may be able to get away with a new seal and bearing (an offset bearing if there is wear on the axle).

The pinion is more difficult, but basically it would be removing the pinion nut, remove the pinion, and check the bearing. Buy a new nut and seal to replace it.

Pay real close attention to the oil that comes out of the diff. Some metal speckling is expected, but not a lot, and especially if there are chunks in the bottom. Look at your gears while you are there too, you may find some problems there as well, and if so you are looking at a complete rebuild or if you are lucky just spider gears.
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Old 09-29-2012, 07:35 PM   #10
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Thanks camarozz! I'll give it a shot this weekend!
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Old 09-29-2012, 10:17 PM   #11
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A very quick and crude way to find out if it is the pinion bearing is to take it for a drive couple of miles will do. Stop get out and feel the rear pumpkin if the snout is noticeably hotter than the rest you will be digging into it soon. Had it happen to my dodge same sounds and it kept leaking gear oil out the axle shaft ends. Finally figured it out and replaced the pinion bearing inner and outer ones. That's a real FUN job LOL
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Old 10-01-2012, 07:56 AM   #12
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I noticed somewhat of the same sound right after i installed a lift. It wasn't making the noise before though. Could the lift be harder on the pinion bearing? It is only a 2-1/2" RC lift.
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Old 10-01-2012, 08:04 AM   #13
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I noticed somewhat of the same sound right after i installed a lift. It wasn't making the noise before though. Could the lift be harder on the pinion bearing? It is only a 2-1/2" RC lift.
in your case I would suspect ujoints first. With a lift you are changing the angle of the drive line and as such changing where the ujoints ride. But you also should feel a vibration of sorts too; but either way I would just change them out if you havent already.

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